INSECTS INJURIOUS TO SMALL GRAINS 



141 



from early May, in Texas, up to the middle of June, in northern 

 Indiana, or about the time the wheat is heading. Their aim 

 at this time is to place the eggs singly in the growing stem, 

 just above the youngest 

 and most succulent joints, 

 which are not so covered 

 by the enfolding leaf 

 sheaths as to be inaccessi- 

 ble to them. Thus it is 

 that the stage of advance- 

 ment in the growth of the 

 wheat stem at the time of 

 oviposition of the summer 

 generation of females 

 determines whether the 

 larvae will be well upward 

 in the straw, and there- 

 fore removed after har- 

 vest, or lower down and 

 consequently left in the 

 field in the stubble. 



" The method of ovi- 

 position and the point 

 where the egg is usually 



formed is shown in Fig. 



_,, . . FIG. 103. Wheat straw-worm, showing 



point where female of the spring form 



gall, nor does it harden deposits the egg in young wheat in early 



iU- u- i -A spring. Enlarged showing position of egg 



the stem within which it a right (Aft W e^r, U. S. Dept. Agr.) 



develops. There is nor- 

 mally but one larva in each joint; but if several eggs have been 

 placed between joints and produce larvae there will be one in the 

 centre of the stem just above the joint and others in the walls just 

 under the internal wall-covering or inner epidermis. These larvae 

 in the walls of the straws do not, as a rule, kill the stem, but 

 their effect is to curtail the yield by reducing the weight. The 

 larvae develop rapidly and reach their full growth before the 



